What Is a Rigid Stranding Line? Applications and Working Principle

The structure of the conductor used in cable production directly affects the electrical performance, mechanical strength, and service life of the cable. Especially in large cross-section power cables, numerous copper or aluminum wires must be brought together in a regular, precise, and controlled manner.

One of the most important systems used for this manufacturing process is the Rigid Stranding Line.

A Rigid Stranding Line is a high-capacity cable production line used to combine copper, aluminum, and aluminum alloy wires at a specified stranding pitch to manufacture multi-wire conductors.

Rigid stranding lines are particularly preferred for the production of power cables, overhead line conductors, large cross-section conductors, and special cable constructions.

What Is a Rigid Stranding Line?

A Rigid Stranding Line is an industrial production system that operates by laying a specified number of wires around a central wire in concentric layers.

The wires are unwound in a controlled manner from bobbins located inside rotating rigid cages. As the wires move along the line, they are brought together around the central wire according to the specified stranding direction and lay length. The finished conductor is then pulled through the line by a haul-off system and wound evenly onto the take-up reel.

This method provides several advantages:

A regular geometric structure is created between the wires.
Conductor diameter and stranding pitch can be controlled.
Large cross-section conductors can be produced.
Production quality and repeatability are improved.
Different cable constructions can be manufactured.

The configuration of a rigid stranding line is determined according to the number of wires, wire diameter, conductor cross-section, material type, and target production capacity.

How Does a Rigid Stranding Line Work?

The rigid stranding process begins by feeding the central wire or conductor core into the line in a controlled manner from the pay-off unit.

The wires unwound from the bobbins inside the rigid cages are guided toward the stranding point. As the cages rotate, the wires are laid around the central wire to form a new conductor layer.

The production process generally consists of the following stages:

1. Wire Feeding

The central wire and the other wires to be stranded are fed into the line in a controlled manner from the pay-off systems.

2. Tension Control

Each wire is maintained at a balanced and stable tension. Tension control is important for maintaining conductor geometry and improving surface quality.

3. Stranding Process

As the rigid cages rotate, the wires are laid around the central wire according to the specified stranding pitch.

4. Forming and Compacting

Depending on the conductor type, the wires can be formed into round or sector-shaped conductors. By using an optional compacting unit, the gaps between the wires can be reduced to obtain a denser conductor structure with a smaller outside diameter.

5. Haul-Off Process

A capstan or caterpillar haul-off system pulls the manufactured conductor through the production line at a constant and controlled speed.

6. Take-Up Process

The finished conductor is wound evenly onto the appropriate reel by the take-up system.

With a PLC- and HMI-based automation system, the operator can control line speed, stranding pitch, stranding direction, haul-off speed, and other production parameters.

Applications of Rigid Stranding Lines

Rigid stranding machines can be used for the production of different wire and cable products. The main application areas include:

Power Cable Conductor Production

One of the most common applications of rigid stranding lines is the production of conductors used in low-, medium-, and high-voltage power cables.

Copper or aluminum wires can be combined to produce conductors in different cross-sections.

The main conductor types that can be produced include:

Round stranded conductors
Compacted round conductors
Sector-shaped conductors
Large cross-section copper conductors
Large cross-section aluminum conductors
Special-geometry power cable conductors

Rigid stranding lines are widely preferred for large cross-section conductor production because of their strong mechanical construction and stable production performance.

Overhead Conductor Production

Rigid stranding lines can also be used for manufacturing bare conductors used in overhead power transmission lines.

These may include:

AAC all-aluminum conductors
AAAC aluminum alloy conductors
ACSR aluminum conductors with steel reinforcement
Overhead conductors with different constructions

The controlled stranding of aluminum wires around a steel core improves both the electrical performance and mechanical strength of the conductor.

Sector Conductor Production

Sector-shaped conductors can be used in multi-core power cables to reduce the overall cable diameter and optimize material usage.

With sector-forming heads or shaping units integrated into the rigid stranding line, round conductors can be formed into a sector shape.

The main advantages of sector conductors include:

Reduced overall cable diameter
Reduced requirement for filler materials
More compact cable construction
Optimized material usage
Better control of total cable weight

Compacted Conductor Production

In compacted conductor production, the objective is to reduce the gaps between individual wires. Compacting equipment positioned after the stranding point applies controlled pressure to the conductor and creates a denser structure.

Compacted conductors may provide advantages such as:

Smaller outside diameter
Smoother surface
Denser conductor structure
More efficient use of insulation material
Optimized cable dimensions

Cable Screening Applications

With an appropriate line configuration, rigid stranding systems can also be used to apply copper or aluminum wires around the cable.

Metallic screening is particularly important in medium- and high-voltage cables, where it helps control the electric field, carry fault currents, and improve electrical safety.

Steel Wire Armoring Applications

Rigid stranding systems can be configured for steel wire armoring in certain cable constructions.

By applying steel wires around the cable core in a controlled manner, the cable gains additional mechanical protection against external impacts, tensile forces, and demanding operating conditions.

Steel wire armoring can be used particularly for:

Underground power cables
Marine and submarine cables
Heavy industrial cables
Mining cables
Special cables exposed to mechanical stress

Main Components of a Rigid Stranding Line

A rigid stranding line can consist of different equipment depending on customer requirements and the product to be manufactured.

A typical production line may include the following systems:

Central Wire Pay-Off

Feeds the wire used at the center of the conductor into the production line in a controlled manner.

Rigid Cages

Carry the bobbins containing the wires to be stranded. Depending on production requirements, cages with 6, 12, 18, 24, 30, or more bobbin positions can be used.

Bobbin Loading System

Helps load bobbins into the rigid cages safely and efficiently. Hydraulic or motorized loading systems may be used.

Tension Control System

Maintains balanced tension in the wires unwound from the bobbins. Stable tension is critical for achieving correct conductor geometry.

Stranding and Die Unit

The section where the wires are brought together around the central conductor and the final conductor shape is formed.

Compacting Unit

Reduces the gaps between wires, decreases the conductor's outside diameter, and creates a denser structure.

Taping Unit

Depending on the production process, separator, semi-conductive, or protective tapes can be applied around the conductor.

Capstan or Haul-Off System

Pulls the finished conductor through the line at a constant speed and helps synchronize the production process.

Length Measuring System

Measures the length of the manufactured conductor and provides production tracking data.

Take-Up System

Winds the finished conductor onto the appropriate reel in a controlled and uniform manner.

PLC and HMI Automation System

Allows production parameters to be controlled, synchronizes the equipment within the line, and enables the operator to monitor the production process.

What Are the Advantages of a Rigid Stranding Line?

Rigid stranding lines offer significant advantages, particularly for large cross-section conductor production.

High Production Capacity

Thanks to their robust mechanical structure and synchronized drive system, rigid stranding lines can provide stable operation at high production speeds.

Precise Stranding Pitch Control

Accurate adjustment of the stranding pitch helps maintain the mechanical and geometric properties of the conductor.

Wide Product Range

Different conductor constructions can be manufactured using copper, aluminum, aluminum alloy, and steel wires.

Modular Line Configuration

The line can be configured according to production requirements with different rigid cages, haul-off systems, compacting units, taping units, and take-up systems.

Automation Support

With a PLC-based control system, production parameters can be easily adjusted, monitored, and repeated.

Heavy-Duty Construction

The mechanical structure is designed for industrial production conditions and supports reliable operation under intensive and long-term use.

Low Maintenance Requirements

Proper mechanical design, high-quality component selection, and regular maintenance can help reduce production interruptions.

What Should Be Considered When Selecting a Rigid Stranding Line?

Selecting the correct rigid stranding line requires evaluating not only machine speed but all technical characteristics of the product to be manufactured.

Before selecting the machine, the following information should be determined:

Wire material to be used
Minimum and maximum wire diameter
Conductor cross-section
Total number of wires in the conductor
Requirement for round or sector-shaped conductors
Compacting requirements
Target line speed
Stranding pitch range
Bobbin dimensions
Pay-off and take-up reel capacity
Taping or screening requirements
Available factory floor space
Automation and recipe management requirements

Selecting a machine that is not suitable for the cable construction may result in capacity loss, quality problems, and unnecessary investment costs. For this reason, it is important to design the line specifically according to production requirements.

AFN Makina Rigid Stranding Line Solutions

AFN Makina develops customized Rigid Stranding Line solutions by analyzing the product structure, production capacity targets, and factory conditions of wire and cable manufacturers.

Lines can be designed according to:

Different wire diameters and conductor cross-sections
Different bobbin and cage configurations
Round and sector conductor production
Optional compacting systems
Optional taping units
Precise tension control
Synchronized drive systems
PLC- and HMI-based automation
Different pay-off and take-up options

AFN Makina's engineering approach covers not only machine manufacturing but also project analysis, mechanical design, production, assembly, commissioning, operator training, and after-sales technical support.

Conclusion

A Rigid Stranding Line is one of the fundamental cable production systems used for manufacturing large cross-section copper and aluminum conductors, power cable conductors, and overhead line conductors.

Thanks to its high production capacity, precise stranding control, modular construction, and adaptability to different production requirements, it helps cable manufacturers establish efficient and sustainable production processes.

If you are planning to invest in a new Rigid Stranding Line or modernize your existing production line, it is important to select a system engineered according to the technical characteristics of the conductor to be produced.

Contact AFN Makina for detailed information about Rigid Stranding Line solutions customized for your production requirements.

Frequently Asked Questions About Rigid Stranding Lines

What does a Rigid Stranding Line produce?

A Rigid Stranding Line combines multiple copper, aluminum, aluminum alloy, or steel wires to manufacture stranded conductors.

What does Rigid Stranding Line mean?

A Rigid Stranding Line is a cable manufacturing system used to strand large cross-section conductors in controlled, concentric layers.

Which materials can be processed on a Rigid Stranding Line?

Depending on the machine configuration, copper wire, aluminum wire, aluminum alloy wire, and steel wire can be processed.

Can a Rigid Stranding Line produce sector-shaped conductors?

Yes. Sector-shaped conductors can be manufactured by using suitable sector-forming heads, dies, and shaping equipment.

Can compacted conductors be produced on a Rigid Stranding Line?

Yes. By integrating a compacting unit into the line, the gaps between wires can be reduced to produce conductors with a smaller outside diameter and denser construction.

Can a Rigid Stranding Line be automatically controlled?

Yes. A PLC- and HMI-based automation system can be used to control line speed, stranding pitch, stranding direction, haul-off system, and other production parameters.

Which cable factories are suitable for Rigid Stranding Lines?

Rigid stranding lines are suitable for facilities producing power cables, overhead line conductors, large cross-section copper or aluminum conductors, screened cables, and armored cables.